Beetle, western pine

The western pine beetle Dendroctonus brevicomis is perhaps the most destmctive insect enemy of western pine forests. The aggregation pheromone is a mixture of the terpenoid myrcene [123-35-3J (163) from the tree and the frass pheromones exo-hsevicomki [20290-99-7] (164) and frontalin [28401-39-0] (165). The Norway spmce beede Ips tppopraphus converts the tree terpenoid myrcene into the frass pheromone ipsdienol [33628-00-3] (166) and the beedes also produce 2-methyl-3-buten-2-ol [115-18-4] and rir-verbenol [473-67-6] (167), all of which are components of the aggregation pheromone. 

Recognising the acetal in frontalin (3), a pheromone of the western pine beetle," is not so easy. Nevertheless, it is Important to look for the two oxygen atoms joined to the same carbon atom ( in 3a) and disconnect the acetal before considering any other steps. 

Frontalin (18), the pheromone of the western pine beetle, is an acetal (atom has two single bonds to oxygen). Disconnection reveals diol ketone (19). 

Dioxalicyclo[3.2.1]octane, or (+)-exo-brevicomin (66), is the aggregating pheromone of the western pine beetle. It has been prepared from glucose using a procedure based on the retro synthesis design shown in Figure 1-2884 ... 

FIGURE 12 18 Relationship between degree of oxidant injury to ponderosa pines and bark-beetle attack (left) and numbers of trees killed by western pine beetle, mountain pine beetle, and the two species together (right). Reprinted with permission from Stark and Cobb. ... 

Recently, M. Asami and T. Mukaiyama 124) synthesized ot-benzyloxyaldehydes (109) having a chiral tertiary center at the ot-carbon atom in high enantiomeric excess by successive treatment of the aminal (102) with diisobutylaluminium hydride (DIBAL-H) and Grignard reagents. The asymmetric reaction is applied to the total synthesis of exo-(+)-brevicomin (110), the principal aggregation pheromone in the frass of the female western pine beetle (Dendroctonus brevicomis). 

The syn alcohol 3, obtained from (R)-( - )-glutamic acid was used for an en-antiospecific synthesis of (+ )-exobrevicomin (4), the aggregation pheromone of the female Western pine beetle. 

It is interesting to note that in the registration process, information concerning the impact on these non-target species, such as the natural enemy community of bark beetles is not required. In both the remedial and preventive modes, the natural enemies are exposed to the insecticides. It has been shown (8) that overall emergence of predators was reduced by 89% and the ratio of natural enemies to the western pine beetle (D. brevicomis LeConte) emergence was reduced by 80% as a result of remedial use of 2% lindane on D. brevicomis. 

Hughes P. R. and Renwick J. A. A. (1977a) Hormonal and host factors stimulating pheromone synthesis in female western pine beetles, Dendroctonus brevicomis. Physiol. Entomol. 2, 289-292. 

Figure 6.11 Biosyntheses of isoprenoid pheromone components by bark and ambrosia beetles from host conifer monoterpenes. (A) Conversion by the male California fivespined ips, Ips paraconfusus Lanier (Coleoptera Scolytidae), of myrcene from the xylem and phloem oleoresin of ponderosa pine, Pinus ponderosa Laws., to (4S)-(+)-ipsdienol and (4S)-(-)-ipsenol, components of the aggregation pheromone (Hendry et al., 1980). (B) Conversion by male and female I. paraconfusus of (1 S,5S)-(-)-a-pinene (2,6,6-trimethyl-bicyclo[3.1,1]hept-2-ene) from the xylem and phloem oleoresin of P. ponderosa to (1 S,2S,5S)-(+)-c/s-verbenol (c/s-4,6,6-trimethyl-bicyclo[3.1,1]hept-3-en-2-ol), an aggregation pheromone synergist and of (1 R,5R)-(+)-a-pinene to (1 fl,2S,5fl)-(+)-frans-verbenol (frans-4,6,6-trimethyl-bicyclo[3.1,1]hept-3-en-2-ol), a compound of unknown behavioral activity for /. paraconfusus. Male and female western pine beetle, Dendroctonus brevicomis LeConte (Coleoptera Scolytidae), convert (1 S,5S)-(-)-a-pinene to (1S,2ft,5S)-(-)-frans-verbenol, an aggregation pheromone interruptant and (1R,5R)-(+)-a-pinene to (1 R,2S,5R)-(+)-frans-verbenol, a compound of...

Bedard W. D., Tilden P. E., Wood D. L., Silverstein R. M., Brownlee R. G. and Rodin J. O. (1969) Western pine beetle field response to its sex pheromone and a synergistic host terpene, myrcene. Science 164, 1284-1285. 

If the reaction depicted in Figure Si3.8 is performed with a slightly modified diene, a dihydropyran is formed which provides the framework for exo-brevicomin, a pheromone of the western pine beetle Dendroctonus brevicomis, and dehydrobrevicomin, a compound which promotes agression in male mice (Figure Si3.9). 

The frass of females of the western pine beetle Dendroctonus brevicomis is enriched with endo- (XIX) and exo-7-ethyl-5-methyl-6,8-dfoxabicyclot3.2.1]octane (XX), which are assigned the trivial epithets endo- and exo-brevicomin (61). Males of 2 brevicomis synthesize 1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane (frontalin) (XXI) in their hind guts (62), and this compound, in combination with the brevicomins and host-derived myrcene, constitutes a potent attractant for both sexes of J). brevicomis (63). Frontal in, also produced by females of . frontalis (62T7 is reported to function as a powerful aggregative pheromone when combined with host monoterpenes such as a-pinene (64). J). pseudotsugae... 

Some of the aggregation pheromones of scolytid beetles also appear to be synthesized with great chiral specificity. The flight response of both sexes of the western pine beetle Dendroctonus brevicomis to (lR,5S,7R)-(+)-exo-brevicomin (XX), host terpenes, and racemic frontal in (XXI) was much greater than the response when the antipode of brevicomin was substituted (160). Similarly, (lS,5R)-(-)-frontalin was a much more powerful attractant than its antipode when tested in admixture with... 

Plant substances are said to enhance some insect hormones, to the advantage of the insect. Bedard et al. (44) have described how the western pine beetle (Dendroctonus brevicomis) uses its host pine trees (Firms ponderosa and P. coulteri) to enhance the drawing power of its sex attractant, exobrevicomin. When ready to mate, both sexes emit the attractant. Bedard found the attractant s power (in terms of numbers of insects attracted) was doubled when mixed with myrcene, a normal constituent of pine wood. Myrcene alone was not attractive. Myrcene, however, is not restricted to pine we have seen earlier (10) that it is consistently found in spruce needles, and in general it is not characteristic of any single group of plants. Since the western pine beetle feeds only on pine, of what real ecological significance is Bedard s report of the enhancement of its hormone by myrcene Why isn t a more specific constituent of pine wood involved Perhaps one is, but research has not yet revealed it. Apart from Brower s work with the monarchs, we have not examined the rich area of herbivore—predator interactions. 

Brevicomin, an aggregation pheromone of the Western pine beetle, is an acetal. Show the structure of the dihydroxyketone that reacts spontaneously to produce brevicomin. 

As another example, let s consider the synthesis of brevicomin, the aggregation pheromone of the Western pine beetle. First, it is necessary to recognize that brevicomin is an acetal and can be disconnected into a diol and a ketone. The diol can be prepared by hydroxylation of an alkene, and the alkene can be prepared by a Wittig reaction ... 

A mass attack of insects can cause serious devastation to crops, forests, food storehouses, etc. These invasions are usually triggered by the release of a set of pheromones. For example, upon landing on a ponderosa pine tree, the female western pine beetle, Dendroctonous brevicomis, releases exo-brevicomin 16 (Scheme 1.5) to attract males. Shortly after mating, the pioneers start to release a mixture of compounds, 17-19, which carries a sort of you are welcome message to their kinsfolk. The flow of incomers increases a hundredfold and as a result the tree is overwhelmed and killed. ... 

Frontalin (98, Figure 4.49) is the active component of the aggregation pheromone of the southern pine beetle (Dendroctonus frontalis), the western pine beetle (Dendroctonus brevicomis) and the Douglas-fir beetle (Dendroctonuspseudotsugae). Mori s 1975 synthesis of the enantiomers of frontalin via enantiomer separation (optical resolution) of an intermediate87 enabled their bioassay, and only (lS,5/ )-98 was bioactive as the pheromone component of D. brevicomis.32 A recent study on female D. frontalis revealed its (15, 5/C)-98 to be of about 91% ee.88... 

This is the most common relationship, and the majority (about 60%) of the chiral pheromones belong to this category. (lR,5S,7R)- xo-Brevicomin (76), the aggregation pheromone of the western pine beetle, and (35,4/ )-faranal (95), the trail pheromone of the Pharaoh s ant, are the typical members of this group. 

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